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ANATOMY & PHYSIOLOGY

In infants, the appendix is a conical diverticulum at the apex of the cecum, but with differential growth and distention of the cecum, the appendix ultimately arises on the left and dorsally approximately 2.5 cm below the ileocecal valve. The taeniae of the colon converge at the base of the appendix, an arrangement that helps to locate this structure at operation. The relationship of the base of the appendix to the cecum is constant, but the tip may be in a retrocecal, subcecal, preilial, postileal or pelvic position, with operative implications. The appendiceal artery, a terminal branch of the ileocolic artery, constitutes the blood supply to the appendix.

The appendix in children is characterized by a large concentration of lymphoid follicles in the submucosa and lamina propria that appear 2 weeks after birth and number about 200 or more at age 15. Thereafter, progressive atrophy of lymphoid tissue proceeds with fibrosis of the wall and partial or total obliteration of the lumen. The appendix historically was considered a vestigial structure, but recent studies have suggested this lymphoid tissue plays a role in the development and preservation of the intestinal immune system.

ACUTE APPENDICITIS

General Considerations

Approximately 7% of people in Western countries have appendicitis at some time during their lives, with data from the Global Burden of Disease 2019 suggesting an even higher rate in central Latin America, central sub-Saharan Africa, and South Asia. With more than 300,000 appendectomies for acute appendicitis performed annually in the United States, it is the most common surgical emergency encountered by the general surgeon and accounts for about 1% of all surgical operations.

Obstruction of the proximal lumen by fibrous bands, lymphoid hyperplasia, fecaliths, calculi, benign or malignant tumors, or parasites has long been considered the major cause of acute appendicitis. Obstruction is not always identified, and a fecalith or calculus is found in only 10% of acutely inflamed appendices. Although evidence of temporal and geographic clustering of cases has suggested a primary infectious etiology, this remains to be proven.

As appendicitis progresses, bacterial overgrowth occurs, with aerobic organisms predominating early in the disease and mixed infection being more common in late appendicitis. This bacterial overgrowth impairs blood supply, leading to the wall of the appendix becoming ischemic and then necrotic. Gangrene and perforation may occur within 24 hours, although the timing is highly variable and some patients may present with symptoms for days and without perforation. Gangrene implies microscopic perforation, bacterial contamination of the peritoneum, and peritonitis. This process may be effectively localized by adhesions from nearby viscera.

Clinical Findings

Acute appendicitis may simulate almost any other acute abdominal illness and, in turn, may be mimicked by a variety of conditions. Progression of symptoms and signs is the rule—in contrast to the ...

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